Solid Solder Deposit (SSD) refers to a relatively thick layer of solid solder metallurgically bonded over the soldering pads, lands or contacts, of a bare-PCB. Bare-PCB refers to a conventional PCB that would require deposition of solder paste prior to components placements for a subsequent reflow soldering operation.
Solid Solder Deposit-Printed Circuit Board (SSD-PCB) refers to a PCB with its soldering pads covered by SSDs. Therefore, a SSD-PCB provides by itself, in solid form, adequate amounts of solder fused to its soldering pads, for reflow soldering components on it.
SSD-PCB technology allows to eliminate defects such as shorts, solder balls and open joints when reflowing PCB-assemblies populated by fine pitch devices. Said devices or components are characterized by spacing between its terminals, or contacts, of less than 0.5 mm.
SSD-PCBs can be optically and electrically inspected before they are accepted for components placement. Therefore, with this technology it is customary to obtain a 100% first-pass yield due to the absence of above cited defects. Those defects are difficult to eradicate when utilizing the conventional paste-printed PCB assembly method. Furthermore, those defects demand costly rework and/or repair.
Since SSD-PCB is an emerging technology it is still relatively more costly than the conventional paste-printed PCB approach for assembling electronics components. Application of SSD-PCB is cost competitive when assembling boards populated by components which solder joints, or terminals, exhibit ultra-fine pitch spacing (herein defined as about 0.3 mm). In lieu of this fact, this invention aims at reducing the overall cost of manufacturing SSD-PCBs, in doing so the SSD-PCB technology would become more competitive than now with respect to the paste-printed PCB approach for assembling electronics components.
The most recent and relevant prior art for producing SSD-PCB is covered by the following ten patents and two pending patent applications;
(1) U.S. patent application Publication No. US 2002/0148881 A1 Process for Manufacturing Solid-Solder-Deposit Printed Circuit Boards published Oct. 17, 2002,
(2) U.S. patent application Publication No. US 2002/0113324 A1 Method for Forming Three-Dimensional Circuitization and Circuits Formed published Aug. 22, 2002,
(3) U.S. Pat. No. 6,158,650 Process for Fine and Coarse Pitch Solder Deposits on Printed Circuit Boards issued Dec. 12, 2000 (PPT™ commercial process),
(4) U.S. Pat. No. 5,984,166 Process for Creating Fine and Coarse Pitch Solder Deposits on Printed Circuit Boards issued Nov. 26, 1999 (PPT™ commercial process),
(5) U.S. Pat. No. 5,492,266 Fine Pitch Solder Deposits on Printed Circuit Boards Process and Product issued Feb. 30, 1996,
(6) U.S. Pat. No. 5,443,671 Product for Surface Mount Solder Joints issued Apr. 4, 1995 (PPT™ commercial process),
(7) U.S. Pat. No. 5,395,044 Apparatus for Forming Surface Mount Solder Joints issued Mar. 7, 1995 (PPT™ commercial process),
(8) U.S. Pat. No. 5,315,070 Printed wiring board to which solder has been applied issued May 24, 1994, (SIPAD™ commercial process),
(9) U.S. Pat. No. 5,310,574 Method for Surface Mount Solder Joints issued May 20, 1994 (PPT™ commercial process),
(20) U.S. Pat. No. 5,271,548 Method for applying solder to and mounting components on printed circuit boards issued Dec. 21, 1993 (SIPAD™ commercial process),
(11) U.S. Pat. No. 5,172,853 Method for applying solder to printed circuit boards and printed wiring board to which solder has been applied issued Dec. 22, 1993, and
(22) U.S. Pat. No. 5,051,339 Method and Apparatus for Applying Solder to Printed Wiring Boards by Immersion issued Sep. 24, 1991 (Optipad™ commercial process).
When this inventor recognized that the presently available commercial technology for manufacturing SSD-PCBs, can and needs to be improved, the objectives and purposes of this invention were inspired, leading him to the conception and accomplishment of this invention.